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Will neuroscience revolutionize the practice of criminal law? Might it fundamentally change the criminal justice system by undercutting the notion of “free will” once and for all?

Not so fast, says Henry (Hank) Greely, a professor at Stanford Law School who specializes in the ethical, legal, and social issues emerging from developments in bioscience. Although the use of neuroscience in the courtroom is promising – and on the rise – today it’s still introduced in a relatively small number of criminal cases. According to research by Nita Farahany at Duke University, only 5% of murder trials and 25% of death penalty trials tap neuroscience. Most often, neuroimaging evidence is used to mitigate punishment, not to challenge “free will.”

As Hank explains in this Worldview Interviews video clip, the law doesn’t actually care about free will, but about whether a defendant committed a crime and had the mental capacity to be held liable for that action. While neuroscientists can measure aspects of a person’s “brain state” at a specific moment in time using fMRI, EEG, and other tools (usually in a laboratory), they cannot correlate that with the “mental state” that caused the person to act in a certain way. Nevertheless, as neuroscience tools and research continue to improve, we’re certain to gain more valuable and reliable insights about the brain and behavior.

The question about whether free will exists is a different matter altogether, and it’s at the heart of long-running scientific and philosophical debates. Are we more than our neurons? That’s an issue we’ll address in a future blog post.

Interested in learning more about neuroscience and the law? Check out these sources: